The Proform c500 treadmill is one of those treadmills made for those people who really don't have a lot of cash, but really want a treadmill. The quality though leaves a lot of space for improvement to put it in a mild fashion.
The most frustrating thing about the Proform treadmills in general is that they never provide the quality that the other brands that ICON Fitness seem to provide, Nordic Track is always one step ahead in terms of flexibility at least.
The warranty is also pretty short and altogether you won't get very much value for your money, but the Proform c500 type of treadmill still does the job. You plug it, you sit on it and you run. Nothing exciting here. The program offer all but the bare minimum required and you will get slightly frustrated if you wish to customize them.
The cushioning system actually does its job pretty well. This is the chapter where Proform designs excel at. Delivering acceptable quality with the cheapest components available. The problem with cheap components is that sooner or later will fail, most likely after the warranty is over, but again they are cheap so the repairing itself won't cost a fortune.
I have actually met people who were quite happy with their Proform c500 treadmill, but these people tend to be the lax type who aren't very picky about their treadmills.
From an outsider's point of view, the design itself is actually good as it provides a fairly good walking area, some decent cushioning and some sturdy handles. Ok, not the handles. They could make them bigger. Right now, it looks like they were designed for the hands of a two year old.
The motor doesn't really stand apart, but it does the job and doesn't sound like a chainsaw cutting steel, so I guess that the Proform c500 treadmills get a plus from this point of view.
Another thing about this treadmill that stands apart is that is not designed for people with a serious weight problem. I mean this in terms of standards, if most of the treadmills have a tolerance of 300 pounds of weight, Proform treadmills only accept 250 pounds. Of course what this means is that the motor will most likely fail if used by a person with a weight problem for a longer period of time.
The stability is quite good even at high speeds and the cushioning remains remarkably reliable if you take it to the extremes.
Altogether, the Proform c500 treadmill is recommended for those in search of a cheaper alternative, but you should be expecting some troubles with it in the long run if you are a power user.